Various navigation systems provide users with turn-by-turn directions. These systems include handheld GPS devices or mobile phones, vehicle-mounted devices, or Internet-based computers with access to applications such as Google Maps. Users input one or more locations and receive a route and turn-by-turn directions. Generally, these systems generate turn-by-turn directions based on static map data, for example, routing users along the biggest roadways or roads with the highest speed limits. These systems may select the fastest route based on the shortest estimated time to travel along the route. Some systems may incorporate traffic conditions, for example reports of congestion, into this calculation. The user may follow the turn-by-turn directions to reach the one or more locations.
Each user requesting turn-by-turn directions is thus provided with the “fastest route” at the time the request is made. However, the actual travel time along the route may vary depending on the accuracy and extent of the traffic information. Traffic conditions may be very time sensitive, that is, the current level of traffic at a particular location may change by the time the user gets to that location. In another example, if a large number of users request turn-by-turn directions between the same two locations, these systems provide the same turn-by-turn directions to each user. Thus, these systems may actually generate additional traffic and the selected route may no longer be the fastest route between the two locations by the time the user is actually on the road.